A known propelling device for an omni-directional vehicle consists of a friction drive device comprising a wheel (main wheel) including an endless annular member and a plurality of free rollers supported on the annular member in a rotatable manner around the tangential axial line of each free roller so that the wheel may rotate both around a central axial line thereof and an annular cross sectional center line thereof, a pair of rotatable drive members provided on either side of the wheel so as to be rotatable around an axial line coaxial with the center of the wheel, a plurality of drive rollers each mounted on the corresponding rotatable drive member so as to be rotatable around an axial line in a skewed relationship to the rotational center line of the rotatable drive member so as to engage the outer circumferential surface of the wheel, and a pair of electric motors for actuating the rotatable drive members around the central axial line thereof. See Patent Document 1, for instance.